This invention relates to the field of nano-technology. Specifically, the invention relates to the one-dimensional growth of nano-crystalline diamond fibers for use in the fabrication of high temperature and high power nano-electronic devices, i.e. biosensors for the electrochemical detection of neurotransmitters.
A nanowire is a wire of dimensions of the order of a nanometer (10−9 meters). Alternatively, nanowires can be defined as structures that have a lateral size constrained to tens of nanometers or less and an unconstrained longitudinal size. Examples of different types of nanowires include metallic (Ni, Pt, Au), semiconducting and insulating; representative materials include, but are not limited to, InP, Si, GaN, SiO2, TiO2, etc.
Typical nanowires exhibit aspect ratios of 1000 or more. As such they are often referred to as 1-Dimensional materials. Nanowires have many interesting properties that are not seen in bulk or 3-D materials since electrons in nanowires are quantum confined laterally; and thus occupy energy levels that are different from the traditional continuum of energy levels or bands found in bulk materials. This quantum confinement is exhibited by certain nanowires, such as carbon nanotubes, which results in discrete values of electrical conductance. There are many applications where nanowires may become important in electronic, opto-electronic and nanoelectromechanical devices, as additives in advanced composites, for metallic interconnects in nanoscale quantum devices, as field-emittors and as leads for biomolecular nanosensors.
Considerable interest has been focused on carbon nanotubes (CNTs) and carbon nanofibers (CNFs) due to their remarkable structural, electrical and mechanical properties. CNFs are grown from the decomposition of carbon-containing gases over metal or alloy surfaces, such as a nanowire, which act as catalysts to the sheets' formation. During the reaction, the carbon-containing gas molecules are adsorbed to certain faces of the catalyst's surface and are subsequently decomposed. Following this, the carbon atoms diffuse through the catalyst particle and precipitate and form successive sheets that stack on one another to form the carbon nanofibers.
Nanocrystalline diamond exhibits high hardness, exceptional thermal conductivity, chemical inertness, biocompatibility, and negative electron affinity. These unique properties make NCD a promising candidate for use as a protective coating with excellent tribological properties; a functional platform for biosensors; and structural material for micro-electro-mechanical systems (MEMS). Particularly, diamond electrodes have attracted considerable interest in recent years due to their superb electrical, thermal and electrochemical properties. However, until now most of the diamond related work is based on a two dimensional form of NCD; in other words, a thin film that is deposited on Si substrate. The question is if we can grow diamond wire just like other semiconductor wires such as Si and ZnO nanowires.
Diamond film has been deposited on metal wires such as Pt or W for electrochemical, biological, and thermal applications. However, the diameter of these diamond coated wires is in the order of hundreds of microns which significantly limits the sensitivity and selectivity of these electrodes.